05.23.12 5:08 PM ET

Usually only the biggest meeting rooms on Capitol Hill are reserved for the most hot-button, highest-profile issues. Hearings for Supreme Court justices, decisions of war, flammable federal scandals. On Wednesday, the Secret Service’s snafu in Colombia was elevated to that level. The agency’s gallivanting officially entered that top level of the nation’s psyche.

From the moment Secret Service Director Mark Sullivan entered the capitol’s largest hearing room, nearly 30 snapping cameras surrounded him. And from early on in the panel’s quizzing of him, the primary questions became clear.

What exactly happened in Cartagena, Colombia, when at least 12 Secret Service agents visited nightclubs and took foreign women back to their hotel rooms? Considering agents are frequently on the road protecting the president and other senior government officials, was this the first time such cavorting happened? And what exactly is the service’s brass doing to rid out such sleaze?

“The last several weeks have been a difficult time for the U.S. Secret Service,” Sullivan somberly told the panel. “Hearing the Secret Service’s credibility called into question has not been easy.”

Many of the revelations of that night in Colombia have already been reported in the media. A dozen agents, in the country last month to protect President Obama during the Summit of the Americas, engaged in heavy drinking and one-night hookups. Some of the women brought back to the hotel were prostitutes, putting the agents in a position to be blackmailed. All of the men had high-level security clearances, sensitive information about the president's schedule, and government equipment.

Complicating the narrative, however, was a Washington Post story from Tuesday night in which anonymous sources alleged similar behavior had happened on other trips, and that the agency informally operates under a “what happens abroad stays abroad” mentality. Sen. Joe Lieberman, the committee’s chairman, cited the story three times and repeatedly questioned Sullivan on whether it was true.

“The thought or notion that this kind of behavior is condoned or authorized is just absurd,” Sullivan said, almost scoffing.

The answer wasn’t good enough. Lieberman and his colleagues wanted to know if agents, when they denied they had ever engaged in similar behavior on other trips, were under oath. “Did you use a polygraph?” Lieberman asked. Sullivan said he didn’t know for sure.

Other senators were more focused on specific details of the episode. Isn’t it strange, Sen. Susan Collins pointed out, that agents used their real names with the women, and when registering the women with the hotel’s “overnight guests” registry?

Sullivan was flummoxed. “These agents did a really dumb thing,” he said. “I can’t explain why they did it. I cannot figure out why they did what they did.”

No one can, really. Not even the agents themselves, whose identities haven’t been publicly revealed. As the Secret Service and the Department of Homeland Security’s inspector general have conducted an internal investigation, several of the agents have been dismissed from their jobs. Others have been suspended pending the end of the full probe.

Since that night in Cartagena, Secret Service officials have instituted several new measures, including a fortified chain of command, as well as a high-level official (a G-15 federal employee, who makes around $150,000 a year) to oversee all foreign trips. Considering that the bad apples have already been removed, Sen. Scott Brown wondered if such an expense was worth it. Sullivan said it was, precisely because it’s the president and vice president’s safety at stake.

Despite the large meeting room, only six senators showed up to interrogate Sullivan. All seemed willing to trust the director’s disbelief and disappointment over the incident—and accept his apology and his insistence that it was, indeed, isolated. “Less than 1 percent of our agents are involved with disciplinary action,” Sullivan said near the end of the session, “which leads me to believe this is not a part of our culture."